We followed the lead of another art teacher and used manilla file folders as the cover. I did not think ahead and have central office save them for me. We just used a box of new ones that I ordered last year.
Students spent several days designing an optical illusion for the cover. If they finished quickly, they could also design the back. We looked at the artwork of Bridget Riley and Vasarley for ideas. I created a slide show and we looked at really cool examples of Op Art. It messed with our eyes. ;-)
Once they were finished, they brought the cover to me and I stapled about 15 sheets of white copy paper, along with a copy of a color wheel for them to color and a shading practice sheet for them to use later.
Even though I ordered 20 packs of the 'school specialty' brand permanent markers, with all 370 students using them at once, they quickly died. Especially the reds and blues. That was extremely frustrating. Other markers did not match the colors quite right. Also, I choose permanent markers in case of spills or splashes. I didn't want their covers to get ruined unnecessarily after all that work.
Even with the bad markers, students still had a lot of success with their designs. I encouraged them to color 'most' of the front. They could use the tan color of their folder as part of the design, just as long as they were filling up the front in a way that looked nice.
*Note: I've noticed that the first page or two that is pressed against the front cover is starting to yellow from the permanent marker ink. Interesting. I'll have to keep that in mind for the future. Maybe we will use colored pencils next year.